A method and a CT unit are disclosed, for example, in the closest DE 198 42 238 A1. This application discloses an image reconstruction recording method for a periodically moving object with the aid of a movement phase and a rest phase by means of a detector unit that is arranged on a gantry and has at least a first and a last detector row, in which:                the first and the last detector row run perpendicular to an axis of rotation and are spaced apart from one another parallel to the axis of rotation by a detector height (D),        the object is displaced along the axis of rotation relative to the gantry at a feed rate, and the gantry is rotated about the axis of rotation at a rotational speed,        at least during the rest phases, per angle of rotation from a group of angles of rotation the detector rows respectively simultaneously record one measured data record each that is assigned to the respective angle of rotation,        the rotational speed is selected in such a way that during a rest phase, the gantry rotates through a rotation angle that is at least as large as a reconstruction angular range required to reconstruct the object,        the feed rate is selected in such a way that the object is displaced along the axis of rotation by at most the detector height during the sum of a movement phase and two reconstruction times, and        the reconstruction time is the time required to sweep over the reconstruction angular range.        
A disadvantage of this method and CT unit is that no cone-beam correction is provided and that, therefore, as the cone angle becomes larger, image artifacts are produced that exert a negative influence on the image quality.
Just as in accordance with the publications DE 198 42 240 A1, DE 197 40 214 A1 and DE 100 63 636 A1, in this method a reconstruction method is applied that requires a reconstruction of data records that provide overall a complete CT image.
Reference is also made to German laid-open patent application DE 102 07 623 A1, which is not a prior publication. This application discloses a method for cardio computed tomography and a cardio computed tomography device in which, for the purpose of scanning an object with the aid of a conical beam emanating from a focus and of a matrix-type detector array for detecting the beam, the focus is moved relative to the object on a spiral path whose central axis corresponds to a system axis, the detector array supplying output data corresponding to the received radiation. Further, for the purpose of imaging an object area executing a periodic movement, a signal reproducing the temporal variation in the periodic movement being obtained during the scanning and images with an inclined image plane being reconstructed from output data respectively supplied during the movement of the focus on a spiral segment. The image planes is inclined with reference to the system axis both by an angle of inclination about a first axis cutting the system axis at right angles, and by a tilt angle about a second axis cutting both the first axis and the system axis at right angles, directly consecutive spiral segments overlapping one another by an overlap angle that is greater than or equal to zero. Finally, the spiral segments are selected taking account of the signal reproducing the temporal variation in the periodic movement such that they correspond to a phase of the periodic movement that is to be imaged.
Although the conical course of the beam between the focus and multi-row detector is taken into account in the method indicated there, the sector data of a plurality of neighboring similar movement cycles being taken into account for constructing the image, the temporal resolution cannot be increased independently of heart rate.
Furthermore, German laid-open patent application DE 101 33 237 A1, which is not a prior publication, sets forth a method for computed tomography and a CT unit in which:                for the purpose of scanning an object with the aid of a conical beam emanating from a focus and of a matrix-type detector array for detecting the beam, the focus is moved relative to the object on a spiral path about a system axis,        the detector array supplying output data corresponding to the received radiation, and the output data respectively supplied during the movement of the focus on the spiral path being divided into output data with reference to subsegments,        segment images with an image surface inclined with reference to the system axis being reconstructed for the subsegments,        a signal reproducing the temporal variation in a periodic movement being obtained during the scanning in order to image an object area executing the periodic movement,        the segment images being assigned a z position on the system axis and a temporal position with reference to the temporal variation in the periodic movement,        segment images belonging to a desired range of z positions and a desired range of temporal positions being selected in such a way that the corresponding subsegments have a total length sufficient to reconstruct a CT image, and        the selected segment images being combined at least indirectly to form a resulting CT image with reference to a target image surface.        
This method also takes account of the conical course of the ray, but the temporal resolution can be controlled only if the table feed is selected to be suitably small during data acquisition.
Finally, reference is made to German laid-open patent application DE 101 27 269 A1, which is likewise not a prior publication and which discloses a method and unit for computed tomography in the case of which, in order to scan an unmoving object with the aid of a conical beam emanating from a focus and of a matrix-type detector array for detecting the beam, the focus is moved relative to the object on a spiral path about a system axis. The detector array supplies output data corresponding to the received radiation. The output data respectively supplied during the movement of the focus on a spiral segment with a length sufficient to reconstruct a CT image is divided into output data with reference to subsegments. Segment images with an image plane inclined with reference to the system axis are reconstructed for the subsegments. The segment images respectively belong to a subsegment being combined to form a component image with reference to a target image plane. Finally, the component images are combined to form a resulting CT image with reference to the target image plane.